<script>

import {ref} from "vue";

export default {
  name: 'Child',
  async setup(){
    let sum = ref(0)
    let p = new Promise((resolve, reject) => {
      setTimeout(()=>{
        resolve({sum})
      },3000)

    })
    return await p
  }
}

</script>

<template>
  <div class="child">
    <h3>我是Child组件（子）</h3>
    {{sum}}

  </div>
</template>

<style scoped>
.child {
  background-color: skyblue;
  padding: 10px;
}
</style>